This invention relates generally to medical methods and devices, and more particularly to methods and devices for removing the lenses from the eyes of mammalian patients.
A. Pathological and Age Related Changes of the Ophthalmic Lens
The lens of a human eye is a crystalline, transparent biconvex structure that serves to focus rays of light on the retina of the eye. The lens consists of a central portion or xe2x80x9cnucleusxe2x80x9d and a peripheral portion or xe2x80x9ccortexxe2x80x9d and is enclosed within a lens capsule. The lens capsule is a bag-like anatomical structure that surrounds the lens and is suspended by fine ligaments that are attached to the ciliary muscles. The ciliary muscles radially stretch and relax the capsule thereby flexing the lens in a manner that varies the optical characteristics of the lens to provide the desired focus for an image. This is commonly referred to as accommodation.
The lens cortex is a jelly-like portion of the lens and is located between the denser inner nucleus and the elastic outer capsule. The lens nucleus is an optically defined-zone which is denser in the central position of the lens. The lens nucleus becomes even denser with age, and can eventually harden and fill increasing portions of the total lens space. Age-related hardening of the lens typically results in a condition known as presbyopia or farsightedness. Additionally the lens may become opacified and/or cloudy. This opacity or cloudiness of the lens is commonly referred to as a cataract.
B. The Pathogenesis and Treatment of Cataracts
Cataracts can be present at birth or can be caused by trauma, toxins, radiation, or certain diseases (e.g., diabetes mellitus). Approximately ninety percent of all cataracts form as a result of the aging of the lens, which can occur as early as age 40. Although cataracts can develop in people at any age, it is a virtual certainty that people who live long lives will eventually develop some degree of cataracts.
The cataractous lens obstructs the passage of light and tends to prevent the formation of a clear image on the retina. Once a cataract develops, it typically becomes more severe over a period of years, though some develop more rapidly. As a cataract xe2x80x9cmatures,xe2x80x9d the initial change is a yellowing in the lens, which becomes cloudy or opacified.
There is one stage in the development of some cataracts when xe2x80x9cnearxe2x80x9d vision actually improves while xe2x80x9cdistancexe2x80x9d vision worsens. This condition is known as xe2x80x9csecond sight,xe2x80x9d when some people can read without their glasses. However, the cataract will continue to progress so that even xe2x80x9cnearxe2x80x9d vision becomes blurred.
Surgery (i.e., surgical removal of the cataractous lens) is currently the only method of restoring vision in a patient who suffers from cataracts. Generally, four types of surgical procedures are known to be useable for removing cataract-affected lenses. These four types of surgical procedures are, as follows:
Extracapsular Cataract Extraction (ECCE): An incision about 10 mm long is made in the lens capsule and the surgeon extracts the harder nucleus of the lens usually in one piece. The softer peripheral portions of the lens are then suctioned out. The typical ECCE procedure results in disruption or removal of a substantial portion of the anterior aspect of the lens capsule.
Intracapsular Cataract Extraction (ICCE): An incision about 15 mm long is made in the lens capsule and the surgeon extracts the whole lens, usually in one piece. The ICCE procedure results in disruption of the zonules so as to detach the lens with its capsule from the surrounding ciliary muscles. At least in the United States, ICCE is no longer a widely used method.
Phacoemulsification (PE): For the phacoemulsification procedure, a limbal or corneal incision of about 3 mm is made allowing insertion of the instrument""s tip into the anterior chamber in a direction almost parallel to the iris. Once the incision has been made, the central part of the anterior lens capsule is typically opened widely to facilitate emulsification of the lens nucleus and cortical clean-up, as well as to provide for an ideal intraocular lens placement into the capsule.
When compared to conventional extracapsular cataract removal procedures, the phacoemulsification technique provides the advantages of a smaller incision, a stronger post-operative globe which reduces astigmatism, better wound closure, lower trauma and quicker improvement in vision. However, this phacoemulsification procedure is contraindicated, except with respect to the most highly skilled surgeon, in patients having a dislocated cataract lens, a shallow anterior chamber, miotic pupils, or low cornea-endothelial cell counts.
Inadvertent perforation of the posterior aspect of the lens capsule during the phacoemulsification procedure can result in vitreous prolapse into the lens capsule. Also, stray ultrasound energy from the phacoemulsification procedure can be destructive to the endothelial cells of the cornea, and can ultimately result in complete degeneration of the cornea.
xe2x80x83i. Endocapsular Phacoemulsification
In a rarely performed procedure, the cataractous lens is removed by an endocapsular phacoemulsification. The cataractous lens must be carved away while not only the posterior side of the lens capsule but also most of the anterior side are left intact. A significant amount of operator skill and training is required to perform endocapsular phacoemulsification. The operator must repeatedly move the ultrasound probe back and forth, while altering its angle, to effect complete emulsification of the lens without causing trauma to or inadvertently perforating the lens capsule.
xe2x80x83ii. Extracapsular Phacoemulsification
Extracapsular phacoemulsification can be performed in the anterior chamber or posterior chamber of the eye. In the case of anterior chamber phacoemulsification, the cataract lens is maneuvered into the anterior chamber where it is carved and removed from the chamber. Anterior chamber phacoemulsification is more traumatic to the endothelial layer of the cornea than posterior chamber phacoemulsification, but it is often an easier procedure for the surgeon to perform. Posterior chamber phacoemulsification consists of carving or shaving the central part of the lens while the lens is still in the lens capsule. This method is more difficult to perform than ECCE due to the possibility of rupturing the posterior lens capsule and exposing the vitreous which fills the volume of the posterior eyeball.
EndocapsularVortex Emulsification (EVE): The procedure is described in applicants"" prior U.S. Pat. No. 5,437,678 (Sorensen), U.S. Pat. No. 5,690,641. (Sorensen et al.) and U.S. Pat. No. 5,871,492 (Sorensen). In the procedure, an EVE probe having a rotating lens-reducing head is inserted into the lens capsule through a small opening of approximately 1-3 mm that is formed in the periphery of the lens capsule. The 1-3 mm opening in the lens capsule may be formed by an electrosurgical capsulotomy device of the type described in U.S. patent application Ser. No. 08/744,404 (Mirhashemi, et al.) The EVE probe is held in a substantially stationary position while the lens-reducing head is rotated. Concurrently with the rotation of the lens-reducing head, an irrigation solution (e.g., balanced salt solution) is gently infused through the probe and excess irrigation solution and debris are aspirated out of the lens capsule causing the nucleus to rotate and thereby coming into contact with the lens reducing head. The flow causes the entire lens (including the relatively hard nucleus) to be repeatedly brought into contact with the rotating lens reducing head and fully emulsified, without the need for substantial movement or manipulation of the position of the probe. In this manner, the entire lens is removed through the small 1-3 mm opening and the anterior aspect of the lens capsule remains essentially intact.
In addition to the ECCE, PE and EVE devices and procedures described hereabove, several other devices and procedures have also been purported to be useable for removing cataract-affected lenses. These other devices and procedures include those described in U.S. Pat. No. 3,732,858 (Banko), U.S. Pat. No. 4,167,944 (Banko), U.S. Pat. No. 4,363,743 (Banko), and U.S. Pat. No. 4,646,736 (Auth).
C. The Pathogenesis of and Treatments for Presbyopia
As pointed out hereabove, the ability of the human eye to change focus depends upon the inherent elasticity of the lens. However, the human lens typically undergoes a gradual loss of elasticity and/or swells with the aging process, thereby causing a gradual decrease in the eye""s ability to focus on objects that are close up. Clinically, this condition is known as presbyopia. Presbyopia occurs to some degree in almost everyone, during the aging process.
Presbyopia has heretofore been treated with prescription glasses or contact lenses. In most cases, a reading correction is required, such as the use of bifocals. However, many patients find bifocals to be difficult to become accustomed to or uncomfortable.
The EVE procedure and apparatus summarized hereabove and described in applicants"" prior U.S. Pat. No. 5,437,678 (Sorensen), U.S. Pat. No. 5,690,641 (Sorensen et al.) and U.S. Pat. No. 5,871,492 (Sorensen) is unique in that it may be useable to treat presbyopia as well as cataracts. This is so because the EVE procedure leaves the main part of the anterior aspect of the lens capsule as well as the ligamentous attachments between the lens capsule and the ciliary muscles, intact. Also, with the EVE procedure no trauma to the endothelium (inner lining of the cornea) is expected because the entire procedure is performed inside the lens capsule. Because the lens capsule remains substantially intact and capable of accommodation, an elastic lens prosthesis can be introduced into the intact lens capsule through the same 1-3 mm opening through which the native lens had been removed by the probe. Thereafter, the normal contractions and relaxations of the ciliary muscles may cause flexing or movement of the lens capsule and resultant changes in the shape of the elastic prosthetic lens, in the same manner as did the crystalline lens before it underwent its age-related stiffening. In this manner, the procedure, in conjunction with a flexible prosthetic lens, may be used as a treatment for presbyopia. This aspect of the procedure, including the introduction of a flexible lens replacement such as a flowable/injectable lens material, are claimed in applicants"" U.S. Pat. No. 5,437,678 (Sorensen), U.S. Pat. No. 5,690,641 (Sorensen et al.) and 5,871,492 (Sorensen).
Currently, there remains a need for further improvement and refinement of the devices and procedures used in for surgical removal of the ophthalmic lens so as to further advance the state of the art and the use of such devices to treat disorders of the eye such as cataracts and presbyopia.
The present invention provides a device for reducing an ophthalmic lens within the lens capsule in a mammalian eye. In accordance with one aspect of the invention, the device includes an elongate probe insertable into the lens capsule. The probe is defined by an outer tubular sheet comprising a hollow bore extending therethrough, and defining a longitudinal axis. An impeller shaft is disposed in the outer tubular sheath and has an impeller on a distal end thereof, wherein an axis of rotation of the impeller is generally coincident with longitudinal axis. The outer tubular sheath is configured and positioned, during operation of the device, such that a distal portion of the sheath will shield a portion of the impeller while allowing a remainder of the impeller to contact and reduce the lens.
In another aspect, the invention provides a device for reducing an ophthalmic lens within the lens capsule in a mammalian eye. The device has an elongate probe insertable into the lens capsule and defining a longitudinal axis. The probe includes an impeller shaft at least partially disposed in a sheath, the impeller shaft having an impeller disposed at a distal end thereof. An axis of rotation of the impeller shaft is generally co-incident with the longitudinal axis of the probe. The device further includes a handpiece having an interior space into which a proximal portion of the elongate probe extends. A drive assembly within the handpiece interior space is functionally connected to a proximal portion of the impeller shaft such that the impeller shaft rotates upon operation of the drive assembly. The drive assembly is adapted to receive non-rotational energy and transmit rotational energy to the impeller shaft.
In a further aspect of the invention, a device for reducing an ophthalmic lens within the lens capsule in a mammalian eye comprises an elongate probe insertable into the lens capsule and defining a longitudinal axis. The probe comprises an impeller shaft having a lens-reducing head disposed at a distal end thereof, wherein an axis of rotation of the impeller shaft is generally co-incident with the longitudinal axis of the probe. A handpiece having an interior space, a front end, and a back end, receives a proximal portion of the elongate probe. Additionally, a pneumatic drive assembly disposed in handpiece interior space includes a turbine, wherein a direct drive connection transfers rotational energy from the turbine to the impeller shaft.
A device for reducing an ophthalmic lens within the lens capsule of mammalian eye accordance with the present invention includes an elongate probe insertable into the lens capsule and defining a longitudinal axis. The probe comprises an impeller shaft having a lens-reducing head disposed at a distal end thereof, wherein an axis of rotation of the impeller shaft is generally co-incident with the longitudinal axis of the probe. A handpiece having an interior space, a front end, and a back end, receives a proximal portion of the elongate probe. A drive assembly is disposed in the handpiece interior space and functionally connects to a proximal portion of the impeller shaft such that the impeller shaft rotates upon operation of the drive assembly. Finally, a translation apparatus at least partially disposed in the handpiece interior space connects to longitudinally displace the drive assembly.
In another aspect, the present invention provides a device for reducing an ophthalmic lens within the lens capsule of mammalian eye including an elongate probe insertable into the lens capsule. The probe comprises an outer tubular sheath having a hollow bore extending therethrough, a hollow impeller shaft having a lumen disposed in the outer tubular sheath and having an impeller disposed at a distal end thereof, an irrigation tube position within and rotationally fixed with respect to the tubular sheath, and a bearing disposed between the impeller shaft and the irrigation tube. The device further includes a handpiece having an interior space into which a proximal portion of the elongate probe extends. A drive assembly is provided for rotating the impeller shaft. An irrigation channel formed within the handpiece interior space is in fluid communication with an annular space formed in the elongate probe between the irrigation tube and impeller shaft. Finally, an aspiration channel formed in the handpiece interior space is in fluid communication with the lumen of the impeller shaft.
In a still further aspect, present invention provides a medical device having an elongate probe insertable into a body and defining a longitudinal axis. The probe has a hollow shaft defining a lumen therein and has a tool disposed at a distal end thereof. An axis of rotation of the tool is generally coincident with the elongate probe axis. A handpiece having an interior space and a front end receives a proximal portion of the elongate probe. A drive assembly disposed in the handpiece interior space is connected to a proximal portion of the impeller shaft such that the shaft rotates upon operation of the drive assembly. An irrigation channel within the handpiece interior space is in fluid communication with an irrigation conduit formed in the elongate probe. An aspiration channel disposed in the handpiece interior space is in fluid communication with the lumen of the impeller shaft. In addition, a fluid block about the impeller shaft between the drive assembly and the handpiece front end provides a barrier between the irrigation channel and the aspiration channel.
In a further aspect of the invention, a variable speed pneumatic turbine system is provided, comprising a turbine in a housing, and a pneumatic system. The pneumatic system includes a pneumatic energy source and a pneumatic delivery line functionally connecting the pneumatic energy source to a orifice in the turbine housing. The orifice is designed to impinge a gas stream from the pneumatic energy source onto the turbine. The turbine system further includes a pneumatic energy controller functionally connected the pneumatic system and capable of controlling delivery of first, second, and third zones of pneumatic energy to the turbine. The first zone comprises pulses of pneumatic energy capable of overcoming stiction of the turbine. The second zone comprises a second zone level of pneumatic energy that is sufficient to sustain rotation of the turbine combined with pulses of pneumatic energy that would overcome stiction if the turbine were to stop rotating. Finally, the third zone comprises a variable level of pneumatic energy that is at least as high as the second zone level of pneumatic energy.
Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.